What would have happened if we would not have had the COVID vaccination?

Marcel Zwahlen, Kaspar Staub

Could the pandemic death toll 2020/2021 have reached the dimensions of the 1918/1919 pandemic?

In mid-2022, the world and thus also Switzerland have entered the third year of the COVID-19 pandemic, caused by the SARS-Cov-2 virus. According to official figures and by end of June, the pandemic has caused more than 6.3 million deaths worldwide since it began, and 13,400 official deaths in Switzerland (which corresponds to 155.1 deaths per 100,000 inhabitants) (table 1). In the meantime, there are various estimates based on excess mortality that the true number of deaths was actually higher both worldwide and in Switzerland. In Switzerland, the second wave in autumn and winter 2020 was particularly fatal, when between October and December the monthly spikes in excess mortality reached historic levels not seen since the 1918 influenza pandemic, just  before the first people were vaccinated in Switzerland at the end of December 2020. These estimates, however, are for a situation in which during 2020 various levels of transmission control measures were put in place, from full shut-downs to less drastic contact reduction measures.

Table 1. Comparison of absolute and relative numbers of deaths between the COVID-19 pandemic in 2020/21 and the influenza pandemic 1918/1919.

	Years	Population (n)	Official deaths (n)	Deaths per 100,000 inhabitants
COVID-19	2020–2022	8,637,000	13,400 [1]	155.1
COVID-19 without vaccination	2020–2022	8,637,000	55,230 [2]	639.5
1918 influenza pandemic	1918–1919	3,753,000 [3]	25,000	666.1

1. As of end of June 2022 (source: www.covid19.admin.ch)
2. Oversimplified back-of-the envelope calculation: 13400 + 41830 averted deaths by vaccination (as taken from supplementary table 3 in [6])
3. Source: Statistisches Jahrbuch der Schweiz 1918

For some time now, studies have been appearing that attempted to estimate both globally and for world regions or countries how many lives the vaccines introduced at the end of 2020 have saved. The most recent of these studies estimated that for Switzerland 41,830 (95% credible interval 33,200–61,730) deaths have been averted by vaccinations until December 2021. By necessity, this estimate is based on various assumptions such as vaccine effectiveness in reducing severe disease (given infection) and transmission. Further assumptions are needed for the level of protection obtained by previous infection, ideally, conditionally by variants of SARS-Cov-2, and the remaining transmission during 2021 and up to the summer 2022.

Obviously, it is hardly possible to take all these factors into account. But if we assume that the order of magnitude of this estimate of 41,830 deaths avoided by vaccination is approximately correct, then a simple back-of-the envelope calculation helps to put the result in a wider context: without vaccination, the COVID-19 pandemic could have cost around 55,230 deaths in Switzerland in 2020/2021 (the 13,400 officially reported deaths to date plus the estimated 41,830 avoided deaths) corresponding to a rate of 639.5 deaths per 100,000 inhabitants.

The next step is to put this into context with the “benchmark” in the history of pandemics in Switzerland over the last 150 years, which is the 1918 influenza pandemic (“Spanish flu”). In historical literature, this is referred to as the greatest demographic catastrophe in Switzerland in the 20th century [1]. In Switzerland it occurred in two or three waves between summer 1918 and spring 1919, depending on the region. At the moment it is unclear to what extent a very strong later wave in February 1920 due to incomplete immunisation should also be counted as part of the pandemic itself. According to contemporary estimates, around 25,000 people died from the 1918 pandemic in Switzerland (in contrast to COVID-19, young adults between the ages of 20 and 40 were disproportionately affected in terms of mortality), and around 65% of the population had contracted the virus at that time [2]. More recent estimates of excess mortality have confirmed this order of magnitude of around 25,000 deaths, corresponding to a rate of 666.1 deaths per 100,000 inhabitants (table 1). So, looking at currently estimated COVID-19 deaths, the “Spanish flu” was about 1.9 times stronger in absolute terms and about 4.3 times stronger in relative terms than COVID-19 (by end of June 2022). But in the hypothetical no-vaccination scenario the mortality rate from COVID-19 might have been similar to the 1918/1919 pandemic (table 1).

But can we so easily say what would have happened without vaccination available from the end of 2020? The answer to this rhetorical question has to be “no”. Constructing a hypothetical world without vaccination depends on many assumptions and, quite likely, if morbidity and number of deaths had remained high – in the absence of a efficacious vaccine – the authorities would have taken other decisions in order to reduce or control the morbidity/mortality impact and the population might have behaved differently. Furthermore, circulating infection would also have increased protection levels and led to slowing of the morbidity/mortality impact, as the 1918/1919/1920 pandemic also showed: at that time, the pandemic faded out after two or three  strong waves (notably caused by a different virus with partly different biological characteristics), and then the pattern changed to seasonal waves occurring every 1–2 years in the 1920s.

Fortunately, we will never have to find out how the COVID-19 pandemic would have played out without vaccination. And this is by no means a final assessment, as we are still in the pandemic and many experts expect increased infection activity again in the upcoming  autumn/winter 2022/2023 season. Moreover, death is only one possible health consequence in any and this SARS-CoV-2 pandemic; as we are now witnessing, COVID-19 survivors often have to deal with longer-term health impairments. That would actually also be one of the constants from the history of infectious diseases: pandemics lead to disabilities. Even though there are mainly anecdotal reports for 1918 that many of those infected recovered badly, felt great fatigue or had heart problems, these other health consequences of the “Spanish flu” have not yet been systematically examined. Therefore, a comparison of these health outcomes other than death between 1918 and COVID-19 cannot be made systematically at this time.

Marcel Zwahlen, Institute of Social and Preventive Medicine, University of Bern, Switzerland 

Kaspar Staub, Institute of Evolutionary Medicine, University of Zurich, Zurich, Switzerland, kaspar.staub@iem.uzh.ch 

 

 

Kaspar Staub was supported by the Foundation for Research in Science and the Humanities at the University of Zurich (grant STWF-21-011).

 

References

1. Sonderegger C, Tscherrig A. Die Grippepandemie 1918-1919 in der Schweiz. In: Krämer D, Pfister C, Segesser D, editors. «Woche für Woche neue Preisaufschläge» Nahrungsmittel-, Energie- und Ressourcenkonflikte in der Schweiz des Ersten Weltkrieges. Basel: Schwabe; 2016. p. 259–84.
2. Eidgenössisches Statistisches Bureau. Die Influenza-Pandemie in der Schweiz 1918/1919. Bull des Schweizerischen Gesundheitsamtes. 1919;29:337–44.